This invention relates in general to an electrical box support but is more specifically directed to the construction at the outer end of the support of a stud-engaging tab that can be bent in the field to conform to a particular box depth and when necessary, straightened and rebent without fracturing the metal forming the tab.
The terms xe2x80x9cboxxe2x80x9d and xe2x80x9celectrical boxxe2x80x9d as used herein are intended to refer to a junction box, receptacle box, switch box, terminal box, connector box or the like as are known in the electrical trade. The term xe2x80x9cstudxe2x80x9d as used herein is intended to include structural members in a building surface, including wall studs, joists, rafters, etc. The term xe2x80x9cwallxe2x80x9d as used herein is intended to include ceiling surfaces as well as vertical walls. With these terms in mind, the teachings of the patents described below are given for background and are deemed to be incorporated herein by reference.
U.S. Pat. No. 1,506,330 issued in 1924 recognized the need for an electrical box support capable of accommodating an electrical box of a known depth and studs of different spacing. The ""330 patent teaches the practice of forming an electrical box support from a pair of telescoping, channel formed struts, each having a face to which the box could be attached. The ""330 patent also teaches bending the ends of the support to form right angled tabs for mounting the box support to and between adjacent studs. The ""330 patent box support however required that adjustments for boxes of different depths be made by locating the bent ends of the box support at different locations on the sides of the studs.
U.S. Pat. No. 1,789,124 issued in 1931 also recognized the need for adjusting the length of an electrical box support by bending the ends of the support to accommodate to studs of different spacing. As with the ""330 patent box support the ""124 patent box support required adjustments for boxes of different depths to be made by locating the bent ends of the box support at different locations on the sides of the stud.
U.S. Pat. No. 2,233,334 issued in 1941 also recognized the need for an electrical box support capable of accommodating electrical boxes of different depth and mounting to studs of different spacing. The ""334 patent teaches the practice of forming an electrical box support from a single bar having a face to which the box could be attached. The ""334 patent also teaches bending the ends of the support to form right angled tabs for mounting the box support between and to adjacent studs. The electrical box support of the ""334 patent however was not adjustable lengthwise and also required that adjustments for boxes of different depths be made by locating the bent ends of the box support at different locations on the sides of the studs.
U.S. Pat. No. 2,788,188 issued in 1957 illustrates in one embodiment an electrical box support constructed of a pair of struts which telescope within each other so as to be able to adjust to different spacings between the studs and providing a face to which the box could be attached. In the mentioned embodiment, the ""188 patent also illustrates the practice of prebending the ends of the telescoping struts to form tabs useful for attaching the box support to and between adjacent studs of a known spacing. In another embodiment, the ""188 patent illustrates an electrical box support formed from a single flat sheet with bendable tabs at each end. Each tab (described in the patent as the xe2x80x9cend of the rodxe2x80x9d) is described as being provided with equally spaced bend lines (described in the patent as xe2x80x9cequally spaced pointsxe2x80x9d) with a weakened area which in the ""188 patent is described as being a grooved, embossed or etched line along which line the tab can be bent back and forth until the tab breaks off. Thereafter, the next adjacent section to the broken point is bent at right angles to the strut to provide a mounting tab. No details are given in the ""188 patent as to how the bend lines would be grooved, embossed or etched. Here it should be recognized that embossing involves forming a protuberance on a surface, etching involves deforming a surface by use of a corrosive and grooving involves cutting into a surface.
The practice of providing a line of holes in an electrical box support to facilitate bending or breaking of the metal along such line, is described in U.S. Pat. No. 4,399,922, issued in 1983, for an electrical outlet box support. The ""922 patent illustrates a pair of weakening lines used to facilitate bending for the purpose of breaking off of excess metal. U.S. Pat. No. 4,483,453, issued in 1984, illustrates an electrical box support in which a plurality of parallel lines of holes are used to facilitate bending for the purpose of breaking off of excess metal and U.S. Pat. No. 4,673,235, issued in 1987, also describes an electrical receptacle subplate having two pairs of such bend lines defined by lines of spaced apart holes. The subplate of the ""235 plate however unlike the bracket of the present invention, does not accommodate to dimensions which may and typically do vary.
The electrical box support described in U.S. Pat. No. 4,967,990, issued in 1990, comprises a pair of telescoping struts adapted to be mounted between two spaced-apart wall studs. The struts described in the ""990 patent have tabs (referred to as xe2x80x9cextensionsxe2x80x9d in the ""990 patent) which can be field bent along either of a pair of fold lines defined by spaced apart slots to accommodate electrical boxes of different depth. U.S. Pat. No. 5,209,444 issued in 1993 describes an electrical box support in both telescoping and non-telescoping form in which the tabs are provided with bend lines defined by spaced apart slots similar to those found in the ""990 patent. U.S. Pat. No. 5,386,959 issued in 1995 is also noted as teaching use of opposed edge slot notches to establish plural bend lines.
Another practical consideration to be noted is that when brackets are prebent at the place of manufacture and arrive at the job site in a prebent form, the installer may find that the tabs of the bracket have been bent at the wrong location and thus will require straightening and rebending. In other situations, the installer may find that he has an excess quantity of brackets prebent for one job site but which are not suitable for the next job site. In still other situations, the customer may change his requirement, e.g. he may need a 2xe2x85x9 inch outlet box at a particular job site instead of a 1xc2xd inch outlet box. These situations thus further illustrate the need for a tab construction which can be straightened and rebent when necessary without fracturing the metal forming the tab.
To complete the foregoing background description it should be recognized that when tabs are bent in the field, it is sometimes necessary after the tab has been bent once along one bend line to straighten and rebend the tab along another bend line better suited to the depth of the box being mounted. For example, the stud to which the tab is being attached may be found to be distorted or the installer may misjudge or initially select the wrong depth of box. In this regard, applicant""s prior U.S. Pat. No. 5,405,111, issued in 1995 teaches in a further example the practice of flattening a previously pre-bent tab and rebending the tab to accommodate a different box depth but without relying on any kind of weakening along the bend lines. Therefore, because of the foregoing described and other situations experienced in the field, it is desirable that the tab be relatively easy to bend to accommodate a particular depth of box but not break apart when straightened after being bent and rebent. However, when a bend line is defined by a grooved, embossed or etched line formed so as to intentionally facilitate breaking of the metal as in the ""188 patent referred to above, by a set of holes as in the ""453 patent referred to above or by a set of spaced apart slots as in the ""990 patent referred to above, bending and straightening of the tab even once after the tab has been bent may and often does result in significant weakening or breaking of the metal forming the particular tab which renders useless the strut of which the tab is a part.
The use of slotted holes along the bend lines has not worked satisfactorily when trying to bend the tabs so as to correspond with a particular desired location. In the manufacturing process, it is known that the narrower the cutting blade of a punch, the more apt the punch will be subject to failure i.e. breaking or chipping. For this reason, the type bracket using slotted holes along the bend lines may typically have, for example, 1xe2x85x9 inch wide by xc2xe inch length slotted hole for each bend line in the tab. Though harder to bend, this type tab construction for a tab typically 1xc2xd inches in width leaves ample steel along the bend line for strong support of the mounted tab. One can also bend and rebend the tab on the bend line without weakening or breaking the tab off. The practical disadvantage of the xe2x85x9 inch wide single slotted hole is that bending the tab creates a large radius bend that originates somewhere within the xe2x85x9 inch wide opening. In other words, the tab length can vary up to xe2x85x9 inch. This could be significant, for if the tab is too short, the outlet box mounted on the bracket of which the tab is a part may break out or bow the sheetrock. On the other hand, if the tab is too long, the user of the bracket may have to purchase longer screws in order to be able to mount one or more electrical devices (i.e. switches, plugs, etc.) to an outlet box.
Another practical consideration arises from the fact that when a tab formed with a single slotted punched opening is bent, the center point of the bend at the bottom of the punched opening may reside on the left side of the tab, whereas the center point of the bend at the top of the punched opening may reside on the right side of the tab (or vice versa). This situation thus may cause one side of the tab to be too long, and the other side of the same tab to be too short. In such circumstances, when the bar bracket is secured to the metal studs, the outlet box will typically not lie in a plane that is parallel to the installed sheetrock. Also to be observed is that one tab may be too long and one tab too short on the same bracket. Also to be noted is that when the tab on the bracket is typically 1xc2xd inch wide and contains a single slotted punched hole xc2xe inch in length, there is only xc2xe inch of steel supporting the bracket at each bend point.
U.S. Pat. Nos. 4,967,990 and 5,209,444 teach other tab constructions in an attempt to compensate for the tab being hard to bend. These patents teach the use of two relatively long slots for each bend line and which effectively remove material at each bend line and make the tabs easier to bend. The problem encountered with this type of slot construction however is that bending and rebending of the tabs at the same bend line may and typically does result in a weakening of the slotted steel. Thus, the tab may break or fail at a future time once installed. When a pair of slots are used to facilitate bending along a bend line, it has also been found that the center line of the bending point can vary from one slot to the next on the same tab. This variation of the center line of the bending point may be as much as xe2x85x9 of an inch and which can make one tab too long and the other tab too short or angle the mounting flange of the tab. Thus once secured with fasteners to the metal studs, the outlet box may not rest in a plane parallel to the sheetrock, or the installer may bow or break out the sheetrock. As stated previously, when the two slots are ⅝ inch in length each and the tab for example is 1xc2xc inches in width, there is only xc2xd inch of steel supporting the bracket at each bend point.
The use of a series of holes to establish a bend line as in U.S. Pat. No. 4,483,453 or U.S. Pat. No. 4,673,235 has also been found not to work satisfactorily. One would encounter the same limitations as with the bracket construction shown in U.S. Pat. Nos. 4,967,990; 5,209,444; or U.S. Pat. No. 5,386,959, depending on the size of the punched holes and the number of holes used to establish the bend line. The punched hole pattern described in U.S. Pat. No. 4,483,453 (FIG. 3), for example, is intended to break apart with little effort. The punched hole pattern described in U.S. Pat. No. 4,673,235 as another example may create a large radius bend that originates somewhere within the punched hole opening. This may in turn cause the mounting tab to be too long or too short, or angled as discussed previously. Thus, there is a need for an improved tab construction having plural bend lines and which permits the tab to be easily bent in the field to form a relatively sharp bend but which can also be straightened and rebent in the field without breaking the metal when necessary because of having chosen for whatever reason the wrong bend line on which to make the original bend.
From the description given, it can be seen that numerous attempts have been made to find a more satisfactory bend line construction that permits in some cases the tab metal to be broken off and in other cases, permits straightening and rebending without risking breakage of the tab metal. Therefore, the primary object of the invention is to provide a further improved electrical box support with an improved tab construction which can be applied to either a telescoping or non-telescoping type support, can be field bent along a well defined bend line to accommodate boxes of different depths and when necessary, can be straightened and rebent along a different but well defined bend line without risk of breaking the metal forming the tab. As previously expressed in the parent patent application Ser. No. 09/621,149, it is also an object to provide a telescoping type electrical box support which has both an improved tab construction that permits straightening and rebending and a relatively tight but releasably locked engagement between the telescoping struts. Other objects will become apparent as the description proceeds.
As previously stated, the improved electrical box support tab construction of the present invention is useful for both the telescoping as well as the non-telescoping type electrical box support. The present invention which is primarily directed to an improved tab construction is described by way of example incorporated in the adjustable support construction of the copending parent patent application, Ser. No. 09/621,149 and as comprising in a first embodiment two and in a second embodiment three struts that are assembled in telescoping relation to accommodate different stud spacing. A tab is provided on each of the outer ends of the support. Lines along which the tab can be bent, referred to as bend lines, are defined by two or more discontinuous score lines formed in each bend line and which weaken the metal along the bend line to facilitate bending but permit straightening and rebending of the tab when necessitated by field conditions and without the risk of substantially weakening or breaking the metal forming the tab. The box support assembly of the present invention as with the invention of the parent patent application, Ser. No. 09/621,149 is also illustrated as being formed of outer and inner struts with a series of interengaging detents, i.e. conical or hemispherical shaped depressions, so that the struts can be moved to relative positions in which the outer strut detents engage and nest into opposed inner strut detents to releasably lock the struts together at some selected length.